Vienna, Austria

ESTRO 2023

Session Item

May 13
16:45 - 17:45
Plenary Hall
Palliation - Oligometastases
Mateusz Spałek, Poland;
Vincent Khoo, United Kingdom
Proffered Papers
17:05 - 17:15
Long-term results of an SBRT dose-escalation trial for bone and lymph node metastases (NCT03486431)
Carole Mercier, Belgium


Long-term results of an SBRT dose-escalation trial for bone and lymph node metastases (NCT03486431)

Carole Mercier1,2, Charlotte Billiet1,2, Ines Joye1,2, Paul Meijnders1,2, Daan Nevens1,3, Piet Ost1,4, Dirk Verellen1,2, Piet Dirix1,2

1Iridium Netwerk, Radiation Oncology, Antwerp, Belgium; 2University Antwerp, Integrated Personalised and Precision Oncology Network, Antwerp, Belgium; 3University Antwerp, Integrated Personalised and Precision Oncology Network, Ghent, Belgium; 4Ghent University, Department of Human Structure and Repair, Antwerp, Belgium

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Purpose or Objective

To present long-term results of a stereotactic body radiotherapy (SBRT) trial for non-spine bone and lymph node oligometastases, comparing toxicity and efficacy of the three most used fractionation (i.e. 5, 3 or single fraction) schedules (NCT03486431).

Material and Methods

This was a prospective non-randomized trial including patients with 3 or less non-spine bone and/or lymph node metastases. In the first, second and third cohort of each 30 patients, all detected metastases were treated to 5 x 7 Gy, 3 x 10 Gy or 1 x 20 Gy, respectively. SBRT could be combined with standard of care systemic treatment. The primary endpoint was 6-month dose-limiting (grade ≥3) toxicity (DLT) rate (previously published) and secondary endpoints were late toxicity, local failure (LF) and progression-free survival (PFS). The study opened in July 2017 and closed in December 2018. In the current report, long-term follow-up was analyzed through September 2022.


Ninety patients received SBRT to 101 metastases. Median age was 69 (IQR 62-75) and the majority of patients (74%) were male. The most common primary tumor types were prostate (n=52; 58%), breast (n=13; 14%) and lung (n=8; 9%). The three groups were well-balanced for patient and tumor characteristics. The primary endpoint was previously reported after a median follow-up of 17.2 months. At that time, no DLT was observed in any of the treatment arms.

Median follow-up for the current analysis was 50 months. Rates of grade 2 SBRT-related acute or late toxicity were 13%,7 % and 10% in cohort 1 through 3, respectively (p=0.9). No grade 3-5 toxicities were observed.  LF occurred in 9% vs 3% vs 6% of lesions for the first, second and third cohort, respectively (p=0.5). Overall estimated 4-year local control rate was 93%. There was no difference in local control rates between schedules (Figure 1).

Median PFS was 16.5 months (95% CI 9.8 - 21.5), with a 4-year PFS of 21% (95% CI 14 - 32). Twenty-one patients (23%) remained long-term disease-free, 33/90 (37%) patients were oligoprogressive (≤3 new lesions) at first recurrence and 36/90 (40%) developed a polymetastatic relapse. Interestingly, median PFS was lower in the group treated with 5 fractions (8 months) compared to both other groups (18 months, p = 0.056) (Figure 2). Median OS was not reached (95% CI 53 months – NA) and 4-year OS was 68% (95% CI 59 – 78).


At long-term follow-up, no new safety signals were observed and SBRT remained entirely safe, whatever the fractionation. Also, local control remained excellent and did not differ between schedules. The overall PFS rate (21% at 4 years) was consistent with the literature. However, while neither intended nor powered for such an analysis, the results might suggest that 3 or single fraction schedules could lead to superior oncological outcomes. Of note, only 40% of patients went on to develop polymetastatic disease, confirming the existence of a true oligometastatic state.